The invention relates to a control device for the drive motor of a windshield wiper device on a vehicle, in particular a motor vehicle, comprising a control circuit that can be activated by a manually operated wiper switch and automatically controls the drive motor in one switching stage of the wiper switch in accordance with a characteristic curve and depending on a signal from a rain sensor.
The control device taken into consideration for the drive motor control of a windshield wiper device in a motor vehicle comprises a control circuit, which can be activated by means of a manually activated wiper switch. The wiper switch assigned to the steering column of the vehicle has a multi-stage design. In a first switching stage of the wiper switch, the drive motor for the windshield wiper device is controlled by a characteristic curve, which is scanned in dependence on the signal from a rain sensor and controls the drive motor accordingly. In the process, the operating data deposited for the drive motor contain the control information that the drive motor is operated intermittently in the starting range of the characteristic curve. Depending on the amount of rain hitting the windshield, which is detected by the rain sensor, the interval time between each wiping cycle is reduced if the rain amount increases. The drive motor is switched to the continuous operation if the value for the interval time falls below a predetermined value, wherein its speed initially is at a minimum. With increasing amounts of rain, the speed is then increased by the control until it reaches a maximum speed with a correspondingly increased number of wiping cycles per time unit.
It is the object of the invention to specify measures for a control device of the type described above, which permit an optimum wiper operation for different influences effecting the vehicle, particularly brightness, temperature, blinding by other traffic participants or light sources and/or driving speed.
This object generally is solved according to the invention by a control device for the drive motor of a windshield wiper device on a vehicle, in particular a motor vehicle, comprising a control circuit that can be activated by a manually operated wiper switch and automatically controls the drive motor in one switching stage of the wiper switch in accordance with a characteristic curve and depending on a signal from a rain sensor, and wherein the operating data for the drive motor can be changed in dependence on the effects of lighting and/or temperature and/or driving speed that act upon the vehicle from the outside. Further embodiments are specified and/or discussed in the description.
In an embodiment of a control device according to the invention, a predetermined standard characteristic curve is replaced with a predetermined limit characteristic curve, depending on light and/or temperature influences that effect the vehicle from the outside, so that the operating data for the drive motor of the windshield wiper can be changed. In particular, a change in the operating data is planned if environmental conditions, gespecially brightness, temperature and/or speed, respectively deviate from a predetermined limit value and in particular if they fall below this value.
The wiper switch is preferably provided with several switching stages for this, wherein the automatic characteristic curve operation is assigned to the first switching stage and one or several fixed speed(s) is (are) assigned to one or several additional switching stages. If the values fall below the limit values for temperature and/or light intensity during the windshield wiper operation, a limit characteristic curve that is changed relative to the standard characteristic curve is provided in the control circuit, wherein the characteristic curves have a fixed upper end point. A preferred limit value for the light intensity in this case is the light intensity that normally exists while the vehicle driving lights are turned on, which results in the danger of blinding. A preferred limit value for the temperature is the temperature around the freezing point because it is to be expected that water mixed with salt hits the vehicle windshield, which can lead to a smearing of the windshield during the wiper operation, thus increasing the danger of blinding and/or reducing the visibility.
The transition from the standard characteristic curve to the limit characteristic curve in that case can occur at least quasi-continuously via intermediate characteristic curves between the standard characteristic curve and the limit characteristic curve. The intermediate characteristic curves, standard characteristic curve and limit characteristic curve all have a fixed upper end point (M). The speed of the transition from a standard characteristic curve to a limit characteristic curve advantageously depends on the degree to which the temperature and/or light intensity deviate from the respective limit values. Thus, the wiper operation is at an optimum if possible even during twilight hours and/or with slowly dropping or increasing temperatures. However, the transition from the standard characteristic curve to the changed limit characteristic curve can also be abrupt.
If the light intensity that affects the vehicle is below a predetermined light intensity, the drive motor speed is increased and/or interval pauses of the wiper operation are shortened and/or the transition from intermittent operation to continuous operation is shifted to lower rain amounts. It is useful if the drive motor speed is lowered for temperatures below a limit temperature and/or the interval pause time of the wiper operation is increased and/or the transition from intermittent to continuous wiper operation is shifted to higher rain amounts. Given a light intensity and temperature below the respective limit values, it is advantageous if the drive motor speed as well as the interval pauses of the wiper operation are increased and/or the transition from intermittent operation to continuous wiper operation is shifted to lower rain amounts. It is particularly favorable if the wiper operation with windshield-washing function is controlled in a corresponding manner.
For one advantageous modification of a control device, an adaptive characteristic curve for the wiping operation is additionally generated, which is changed by means of manually operated control means if it does not meet the individual requirements of the motor-vehicle user. For this, the pause time between two wiper operations can be changed during the intermittent operation and/or the drive motor speed or the wiping frequency can be increased or lowered during the subsequent, continuous wiper operation. The wiper switch is preferably provided with the standard three switching stages, wherein the automatic characteristic curve operation is assigned to the first switching stage, while one or several fixed speed(s) is (are) assigned to the one or several additional switching stage(s). The operating data predetermined by the manufacturer for controlling the drive motor for the windshield wiper device are programmed to meet average requirements. After switching on the automatic characteristic curve operation, an intermittent operation with long pause times is controlled automatically for small rain amounts, depending on the amount of rain per time unit that is detected by a rain sensor. The pause times will decrease with increasing amounts of rain. If the rain amounts increase even further, the drive motor will change to a continuous operation, wherein the speed is increased up to a maximum value if the amount of rain increases accordingly.
If the specified characteristic curve does not control a wiper characteristic that meets the personal ideas of the driver, the characteristic curve can be changed by switching on additional switching stages of the wiper switch. If, for example, the pause times during the intermittent operation are too long or the wiper frequency during the continuous operation is too low, the wiper switch must only be switched to one of the additional stages with the fixed, predetermined speeds. This switching measure is recorded in the control unit and the slope of the characteristic curve is reduced by means of an adaptation algorithm control, triggered by this measure. The end point of the characteristic curve remains at least for the most part fixed in the maximum operating point of the drive motor. As a result of this pivoting upward of the characteristic curve, around the maximum operating point, the operating data assigned to this characteristic curve for the drive motor are changed in such a way that the pause times during the intermittent operation are respectively shortened and the drive motor speed or the windshield wiper wiping frequency in the characteristic curve segment of the continuous operation is raised. A switching of the wiper switch from stage 1 to stage 2 can cause a specified change. In contrast, a switching through from stage 1 to stage 3 makes it possible to control a stronger raising of the characteristic curve. As a result of a repeated switching back and renewed switching up of the wiper switch, a stage-by-stage raising of the characteristic curve or the stage-by-stage reduction of the increase by means of the algorithm control can be effected. A switching back of the wiper switch to the first switching stage for the automatic operation thus always makes available a characteristic curve that approaches the driver needs for a rain-dependent control of the windshield wiper device.
On the other hand, if the operating data supplied to the drive motor by the rain-dependent operating point data result in a wiping sequence that is too high for the individual requirements of the driver, the data for the characteristic curve can be changed back through a steeper increase in the slope of the characteristic curve, longer pause times for the intermittent operation, and a slower wiping frequency in the superimposed characteristic curve range. It is assumed that the actual characteristic curve for the automatic, rain-amount dependent operation is actuated in a range that is above the number of wiping cycles or the drive motor speed and is fixedly predetermined by position 2 of the wiper switch. Thus, if the user of the wiper switch switches from the switching position 1 for the automatic operation to the switching position 2, the operating data specified by the switching position 2 are below the data specified by the actual characteristic curves. The control signal obtained in this way causes a reduction of the operating data in the algorithm control, not only for this operating point, but for the complete characteristic curve. In the process, the operating point of the characteristic curve, which is assigned to the highest, detected rain amount, remains again unchanged. A new characteristic curve can be determined for this in each case, or it is possible to switch to one of several fixedly predetermined characteristic curves. Furthermore, if the wiper switch is turned to the zero position during the operation and the rain sensor still signals a rain amount worth mentioning to the control circuit, a control command obtained in this way can be used to change the slope of the characteristic curve or to change the curve course, such that the pause times during the intermittent operation are increased and the continuously occurring wiping cycles in the upper range of the characteristic curve are reduced.